‘Extraterrestrial’ : Rare space-derived plutonium found in deep ocean crust

Scientists have discovered plutonium-244, a very rare heavy metal from space, in the deep ocean crust, shedding light on how heavy metals form in stars.
The plutonium-244 isotope found in the deep ocean may have arrived on Earth along with iron-60, a lighter metal formed during supernova explosions. The finding suggests that both heavy metals could have been produced simultaneously during a supernova explosion, although other events are possible, such as a neutron star merger that could form a portion of the plutonium-244.
Understanding how nature forms heavy elements is one of the three most important questions in physics, with half of the elements heavier than iron being formed in the central regions of stars through a very well understood fusion process, while the other half requires a high density of free neutrons to form. That means they would have to have formed in a much more explosive environment than a typical star core, perhaps a supernova or a massive event like a neutron star merger.
Researchers are interested in the wreckage cosmic objects found on earth signs, some radioactive contamination of heavy metals are not naturally formed on earth, especially the researchers are looking for plutonium – 244, it has a half-life of 80.6 million plutonium variant, which means that the radioactive element decay need to consume 80.6 million after the first half of the plutonium. They found that any plutonium-244 that was present during earth’s formation had decayed long ago, so any plutonium atoms they found could have come from another planet.
Can we find plutonium-244 on Earth? If it can, then we must know it is an extraterrestrial visitor.
Rare metal
To look for these rare metal atoms, the researchers searched deep in the crust 1,500 meters below the Floor of the Pacific Ocean. The results showed that rock layers beneath the deep ocean crust form very slowly. One millimeter crust records 400,000 years of history.
The researchers then detected samples of iron-60 (iron formed in supernova explosions) and plutonium-244. Finding iron-60 was not surprising, since studies had found fluctuations in the iron-60 index in deep-sea sediments and in the crust. This latest finding confirmed what researchers had suspected: There were two increases in the Iron-60 index — one between 55 million and 4.2 million years ago, and another at some point 7 million years ago. The influx of metals may have been the result of two relatively recent supernova explosions.
The process that produced iron-60 in a supernova must have been spectacular, as bright as a full moon is today, so the explosion could have been seen directly during the day.
Previously, researchers lacked a sensitive method to accurately count the number of extremely rare plutonium-244 atoms scattered throughout the earth’s crust, but in the latest study, they used cutting-edge technology and methods, and finally they did. At present, it is difficult to determine precisely when this extraterrestrial plutonium arrived on Earth, because researchers must search for layers of the earth’s crust 5 million to 3 million years ago. However, the influx of plutonium-244 is closely related to the influx of iron-60.
A supernova explosion?
Although the arrival of both plutonium-244 and iron-60 at the same time suggests they may have both come from supernova explosions, scientists still have a lot of doubts. Attempts to use computers to simulate the formation of heavy elements in supernova explosions have finally come to light. The ratio of iron-60 to plutonium-244 found in this latest study suggests that after the star has exploded, Plutonium-244 is much less abundant than iron-60 and is probably only a fraction of the element formed after the explosion.
Perhaps the plutonium-244 atoms found in the deep ocean crust didn’t come from a supernova explosion at all. Instead, plutonium-244 may have originated from an earlier astronomical event, when a shock wave containing iron-60 headed toward Earth pushed the heavier plutonium-244 across the earth’s surface, where it most likely drifted aimlessly in deep space. In that case, both elements would have reached Earth at the same time, but plutonium-244 is much older.
To explore this possibility, the researchers hope to look at different kinds of atoms with different half-lives, which act like a clock, so scientists can determine the estimated range of age when the element was formed. For example: If plutonium-244 is found with an element with a shorter half-life, both elements are “younger and fresher.” The study also found that less plutonium-244 was produced by supernovae, and that most of the plutonium-244 found on Earth may have originated from other astronomical events, such as neutron star mergers.
Now, researchers are beginning to study a larger area of the earth’s crust. Surveying a larger area of the earth’s crust will expand the researchers’ search for plutonium-244 and get an accurate timeline of when those atoms arrived.